1. Field of the Invention
The present invention relates generally to vehicle frame assemblies. More particularly, the present invention relates to a frame assembly for a scooter-type vehicle.
2. Description of the Related Art
Scooter-type vehicles, or scooters, include a frame assembly, which usually supports a body of the scooter, along with front and rear wheels of the scooter. Typically, front and rear suspension assemblies are operatively positioned between the front and rear wheels and the frame assembly. The front suspension assembly commonly is a telescopic fork arrangement, while the rear suspension assembly is a swingarm-type arrangement. In a scooter, the rear suspension swingarm typically supports a power unit, which is configured to drive the rear wheel of the scooter. The power unit may include a torque-producing device, such as an internal combustion engine or electric motor, along with a transmission and final drive assembly, such as a drive shaft, drive belt, or chain and sprocket assembly, for example.
The frame assembly of a scooter-type vehicle is an elongate structure, which typically extends from a forward end to a rearward end of the scooter. A scooter frame assembly generally is convex in shape, as viewed from a side elevational view. A handlebar assembly and a seat assembly are supported at opposing ends of the frame assembly and a generally open area is defined therebetween. Accordingly, the open area between the handlebar assembly and the seat assembly allows the scooter to be easily straddled, or mounted, as opposed to a typical motorcycle, wherein a fuel tank occupies the space between the handlebar assembly and the seat assembly. Such an arrangement may be referred to as a “step-through” frame assembly.
Generally, a scooter frame assembly is constructed of a welded-up assembly of individual tubular members. Typically, a central portion of the frame assembly includes a pair of upper tubes, or rails, and a pair of lower tubes, or rails. The individual pairs of upper and lower rails usually are aligned with one another in a vertical direction and spaced from one another in a lateral direction, with the pair of upper rails being spaced above the pair of lower rails. Various large components of the scooter are housed within an internal space defined by the upper and lower rails. For example, a radiator and fuel tank of the scooter typically are supported within the space between the upper and lower rails. As a result of the welded-up construction of the frame assembly, assembly of the components within the space defined between the upper and lower rails is difficult. Accordingly, the overall cost of the scooter is increased due to the time required for assembly.
Furthermore, the frame assembly of a scooter-type vehicle is relatively long compared to that of a normal motorcycle because of the rearrangement of the components in order to achieve the step-through construction of the frame assembly. That is, typically the fuel tank and the engine are aligned in succession along a longitudinal central plane (length) of the scooter, between the front and rear wheels, as opposed to a typical motorcycle wherein the fuel tank is positioned above the engine. Because the frame generally is longer to accommodate both the fuel tank and engine, it must also be strengthened to resist lateral or torsional forces that may be applied to the vehicle while turning. In order to achieve a desired level of strength, the frame assembly of a scooter typically is constructed from relatively thick steel tubing, which results in the overall frame assembly being relatively heavy.